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dehumidifier?

post #1 of 8
Thread Starter 
Im looking for a feasible way to use sub 0 temps for 24/7 where the humidity seems to be the biggest issue.. So i figured maybe if i insulate the motherboard environment (like airtight in ambient pressure) and run a ventilation loop from that environment through a dehumidifier it might solve the problem. Problem is - ive never owned nor even seen (i think) a dehumidifer so i have no clue how effective they really are, could they possibly do the trick here?
post #2 of 8
I used to have one at a shop I worked at (I used to wash dogs). It was pretty noisy and I dont think you would be able to stand the noise right next to your computer for too long. Not to mention they use a lot of electricity so be prepared to see a nice increase in your electric bill.
post #3 of 8
Quote:
Originally Posted by hazarada View Post
Im looking for a feasible way to use sub 0 temps for 24/7 where the humidity seems to be the biggest issue.. So i figured maybe if i insulate the motherboard environment (like airtight in ambient pressure) and run a ventilation loop from that environment through a dehumidifier it might solve the problem. Problem is - ive never owned nor even seen (i think) a dehumidifer so i have no clue how effective they really are, could they possibly do the trick here?
I am not commenting on the cost and noise factors of this plan but just on the technical aspect.

I think the best top grade consumer home use dehumidifier can drive the RH of an enclosed environment to 30%.
So, suppose you put the motherboard in an airtight environment to use such a dehumidifier and further suppose you do not cool down the air inside the sealed environment, the air temp will be more or less like the ambient air outside the environment (say, 20C).

At 20C and 30% RH, dew point is 2C. I do not know how far below 0C that you are planning to go. But I think if you deal with LN2, condensation is still a threat in such environment.
post #4 of 8
household dehumidifiers are basically air conditioners, except they rearrange the evaporator and condenser. The air is first cooled by the evap to around 0C or thereabouts, water condenses on the evap and runs to a drain. Ice may form, and the unit will shut down and defrost itself. The cooled air is sent over the condenser coil and heated back up before it is discharged into the room. A household dehum cannot get the room dewpoint lower than it's own evaporator temperature. So maybe you could get barely to 0C without risking condensation.

If you use a household dehumidifier you couldn't operate sub zero, basically you can only go as cold as the dehum. gets. Going colder will result in condensation. If a dehumidifier were equipped with a defrost cycle and designed to go very cold, it could build ice on it's evap and get the dewpoint lower than 0C, and likely however low you want. That's not necessary for a household type, and I think that'd be a commercial or laboratory unit, and big $.

You might be able to rig something up with a self defrosting freezer. All commercial (restaurant) freezers are self defrosting, and a lot of residential freezers are too.

If you create a fairly well sealed closed loop air space and dehumidify it, it might work.

You might also just purge the air with nitrogen and setup a regulator to keep a tiny positive pressure inside.
Workshop Heater
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Workshop Heater
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post #5 of 8
Thread Starter 
from what i understand most dehumidifiers work via phase change as in they catch water particles by dropping them out of the higher temperature air on a cooling element and then get rid of them in some mechanical way so theoretically i think if i'd just let it run the efficiency would drop as the air gets less humid but theoretically there shouldn't be a limit as to how much water could be removed (obviously it would never reach 0 but if i can get low enough so it wouldnt form a water droplet upon condensation thats good enough)
post #6 of 8
No, there is a limit, it's the temperature of the evaporator in the dehumidifier. The best they'll do is get the air dewpoint down to about 0C.

If you place a surface with a temperature of -1C in contact with air that has a 0C dewpoint, you'll get condensation.

The efficiency doesn't drop that much as water is removed from the air, the dehumidifier will still be running a refrigeration compressor to cool air down, and then heat it back up with the condenser.
Workshop Heater
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Workshop Heater
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post #7 of 8
cut out the middle man : insulate your mobo and use the evap to cool/chill a w/c loop.
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Lil Cutey
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post #8 of 8
Thread Starter 
Quote:
Originally Posted by MightyMission View Post
cut out the middle man : insulate your mobo and use the evap to cool/chill a w/c loop.
that would be introducing the middle man

Quote:
Originally Posted by DetroitAC View Post
No, there is a limit, it's the temperature of the evaporator in the dehumidifier. The best they'll do is get the air dewpoint down to about 0C.

If you place a surface with a temperature of -1C in contact with air that has a 0C dewpoint, you'll get condensation.

The efficiency doesn't drop that much as water is removed from the air, the dehumidifier will still be running a refrigeration compressor to cool air down, and then heat it back up with the condenser.
i should be able to use the same heat pump for both dehumidifying and cooling then - have 2 blocks (for example), use 1 for cpu and second for running the ventilation through (and ill have to find some way to rid myself of the product) so after sealing the case i dryrun the dehumidifying block and remove the product until no significant amount forms and then switch over to the cpu block and consider the insides condensation safe. Since the cpu block has to fight with the cpu's thermal output it will never be as cold as the uncontested dehumidifying block

are there any other significant durability issues from running around -30C cpu in a room temperature environment? like cold shrinkage or something
Edited by hazarada - 8/3/11 at 11:11am
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